Does it mean the frozen potato wedges you can find in supermarkets, or does it mean fresh potatoes that I've cut into wedges (if so, does that include/exclude the skin, or is that optional?)
"Ready-Prepared" typically means a packaged product. Many 'ready-prepared' potato products are par cooked and coated lightly in oil before freezing, so cutting your own may be a problem.
A specific recipe would be useful, so that we can give recommendations on how to deal with freshly cut potatoes (par cook vs. adjusting time/temperature of the whole dish)
Potato wedges are potato wedges, whether you cut them up yourself or purchase them already prepared. Depending on the recipe and personal preference, skin is optional. Recipes call for "ready prepared" ingredients when the author is attempting to save you time. So, in this case, it probably means store-bought, already prepared wedges. Really, it takes little time to peel and wedge a potato. Plus you will be able to get a fresher product, and it will probably cost you less. Of course, you may have to alter cooking time, depending on whether or not the prepared item is already cooked.